Method for suppressing coherent noise in seismic data

Abstract

A method for removing boundary-generated artifacts in synthetic and actual seismic data. After seismic data processing, undesirable boundary-generated artifacts appear in the final seismic section. To remove this unwanted noise from the section, zeros are added to the lower boundary of the seismic section. This essentially pushes the sources of the noise downward in time in the section. After padding with zeros, the seismic data is collapsed to their point sources of origin using the Stolt migration/diffraction algorithm. Once the data are collapsed, the size of the seismic section is reduced to its original size. Following the resizing of the section, the inverse of the earlier applied Stolt algorithm is applied to return the seismic data to its original form, minus the boundary-generated artifacts.

We claim as our invention: 
     
       1. A method for removing artifacts from data in a seismic section, comprising the steps of padding the data with zeros at a lower boundary thereof, collapsing the data to their point sources of energy, reducing the size of the seismic section to its original size before padding with zeros, and reversing the step of collapsing to restore the data to its original form. 
     
     
       2. The method of claim 1, further comprising the step of previously precessing the seismic data, correcting for normal move out, spherical spreading and dipping and folded reflectors. 
     
     
       3. The method of claim 1, wherein the step of padding with zeros comprises the step of introducing zeros to the lower boundary of the seismic section, thereby moving the point sources of the artifacts downward and out of a zone of valid seismic data. 
     
     
       4. The method of claim 1, wherein the step of collapsing the seismic data to their point sources of energy comprises the step of applying an algorithm, thereby causing diffraction semicircles of an artifact to collapse to its apex. 
     
     
       5. A method for removing boundary-generated artifacts from a seismic section generated during data processing, comprising the steps of: (a) padding the seismic section with zeros to move the artifacts downward, approximately doubling the size of the seismic section;   (b) collapsing the artifacts to a point source of origin;   (c) reducing the size of the seismic section back to its original size thereby omitting the artifacts; and   (d) reversing step (b) to transform the seismic section back to its original form absent the artifacts.   
     
     
       6. The method of claim 5, wherein the step of collapsing the artifacts to a point source of origin is comprised of the step of applying a diffraction algorithm to the seismic section. 
     
     
       7. A post-processing method for removing noise generated by artificial boundaries in a seismic section, comprising the steps of: (a) enlarging the seismic section by padding with zeros to move the noise downward;   (b) collapsing the noise to a point source of origin;   (c) reducing the size of the seismic section to exclude the noise; and   (d) reversing step (b) to place the seismic section in its original form absent the noise.   
     
     
       8. The method of claim 7, further comprising the step of substantially processing the seismic section, correcting for normal move out, spherical spreading and migration, prior to the step of enlarging the seismic section with zeros.